I don't really understand the significance of Crispy's location either if you could spell it out once more..
I can only think Nigel was disputing that the BT operative heard Crispy barking. As Crispy may not be heard in a possible locked bedroom. Although there is no evidence both of the main bedroom doors were shut.
Reply 11 dismisses Nigel's theory with 16 reasons.
There is no reason why the police would ask a BT operative to lie. A barking Crispy does not assist a police framing attempt in any way.